Skin protection against ultraviolet (UV) radiation has long been crucial due to its role in photoaging, sunburn, and wrinkles. This study focuses on developing a bio-based sunscreen from Calendula arvensis capitula extract. Various extraction methods (maceration, sonication, and infusion) and solvents (EtOH, EtOH-H2O, and H2O) were explored in order to identify the most effective extract for use in a sunscreen formulation. Each extract was analyzed for its phenolic content, as well as antioxidant activities (assessed through DPPH, CAT, and FRAP assays). Enzyme inhibition assays for tyrosinase, elastase, and collagenase highlighted the low IC50 values of the hydroethanolic extract. Furthermore, the in vitro sun protection factor (SPF) against UVB radiation was measured using ultraviolet spectrophotometry. A phytochemical analysis showed phenolic levels between 8 and 27 mg GAE/g, flavonoid concentrations of 7–13 mg QE/g, and tannin levels of 1.15–1.68 mg/mL, alongside moderate antioxidant activity. The ethanol maceration extract reduced the interfacial tension to 2.15 mN/m in 600 s, outperforming the conventional emulsifier polysorbate 20. The sonicated hydroethanolic extract demonstrated remarkable SPF efficacy (SPF = 193.65 ± 0.02), far exceeding that of the standard zinc oxide (SPF = 11.88 ± 0.03). The proposed formulations meet the COSMOS standards, suggesting their potential for certification as biological products. Further clinical and in vivo studies are necessary to confirm their safety and commercial viability.
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